Disclaimer: This is all personal opinion and I'm not a drugs expert. I'm kind of an idiot. Read at your own peril.
I guess I fall into this category (although I will occasionally smoke a bit of weed if there is weed present and the joint's already being passed around. I'm talking 2-3 times a year tops). Apart from alcohol and the occasional spliff I have absolutely no interest in doing drugs. I believe they should all be legalised, in order to be regulated and bought safely without dangerous impurities. But I have no interest in doing or trying any of them. I was only willing to give weed a chance because I knew that it was not dangerous or addictive - at least not in the way that alcohol is (and that's legal!). It is mind-altering but it is not dangerously so. People can still become insufferable potheads who revolve their entire personalities around smoking weed, but I'd much rather deal with an unsufferable pothead than a strung out junkie who only cares about their next fix. That said, I know dozens of people who smoke weed on a regular basis who are fully normal functioning people.
Morally I have no stance against drugs, but I would still flip out if somebody I knew started getting into heroin or meth or any of those highly addictive substances, because they can quickly cause your life to spiral as you let the addiction take over. This is hypocritical of me since I enjoy alcohol and that too can destroy lives... but it's not drugs I'm against - it's people ruining their lives.
I have a cousin who almost lost her life because of heroin. Luckily she's now been clean for over a decade, but it has done irrepairable damage to her in every single way. It destroyed her family, she went to prison and almost lost her leg. Long after she got clean it left permanent scars, both visible and invisible, though she is doing much better these days.
Alcoholism can do the same though and the only real difference is that one drug is legal and the other is not. Also people can drink alcohol without becoming addicted, but alcoholism is a genetic predisposition and you never know if you're going to be in that group or not until after you start to drink (plus traumatic life events and such could propel one towards alcoholism).
Then there's drugs like ecstasy. Ecstasy is a murky area for me. I'm absolutely not interested in trying it, but my boyfriend and his circle of friends take MDMA in powder form quite often at parties (maybe once or twice a month). I wouldn't say any of them are addicted to it - they're just happy go lucky hedonists who like to party and that's fair play! They've never done anything worse than ecstasy and hopefully that's not about to change, haha. They all hold down good jobs. They just do it at home too - no danger of dehydration from dancing for 12 hours straight. I could easily go along and try this too, but I'd rather just stay home and have a quiet evening because I'm a bit of a hermit. I also don't trust myself with drugs and I don't want to lose control, as it were. Weed is as adventurous as I'm ever going to get and even then I only smoke a couple of times a year.
Cocaine is probably on a similar level to heroin for me - I mean, I know people who have done cocaine on occasion and not become addicted to it, but it's still an addictive substance and I've also seen it destroy peoples' lives. I would put it firmly on my "no-no" list. It also seems like a stupid drug. Why go through the pain of snorting something up your nose for a high that lasts maybe 10 minutes tops? Not to mention it's extremely costly. Ergh. Screw cocaine.
Then there's stuff like cough syrup or other weird things like painkillers... nah. Fuck that stuff too. Not worth it. I'm not interested in having an "amazing experience", in fact, the more normal I keep myself the better for my brain. I suffer from anxiety and drugs would only throw a wrench into the careful tightrope I'm walking to make sure I feel normal, calm and happy on any given day. The only reason I even drink alcohol is because I already know exactly what that's going to do to me, so there are no surprises. I hate surprises! I like being able to keep control of my mind. As for weed, it is mind-altering, but it doesn't change my personality and again I know what to expect. So that's acceptable to me too.